The canning of fruits and vegetables is a growing, competitive industry, especially in the U.S. for export. The industry is made up of establishments primarily engaged in canning fruits, vegetables, fruit and vegetable juices; processing ketchup and other tomato sauces; and producing natural and imitation preserves, jams, and jellies. Typical canned products include beans (cut and whole), beets, carrots, corn, peas, spinach, tomatoes, apples, peaches, pineapple, pears, apricots, and cranberries. Typical juices are orange, pineapple, grapefruit, tomato, and cranberry. The term canning includes preserving in actual cans as well as bottles and jars, among other containers.
One key objective of food processing is the preservation of perishable foods in a stable form that can be stored and shipped to distant markets during all months of the year. Processing also can change foods into new or more usable forms and make foods more convenient to prepare. Consequently, one goal of the canning process is to destroy any microorganisms in the food and prevent recontamination by microorganisms. Heat is the most common agent used to destroy microorganisms. Removal of oxygen can be used in conjunction with other methods to prevent the growth of oxygen requiring microorganisms.
A typical commercial canning operation may employ the following general processes: washing, sorting/grading, preparation, container filling, exhausting, container sealing, heat sterilization, cooling, labeling/casing, and storage for shipment. One of the major differences in the sequence of operations between fruit and vegetable canning is the blanching operation. Most of the fruits are not blanched prior to can filling whereas many of the vegetables undergo this step. With many fruits, preliminary treatment steps (e. g., peeling, coring, halving, pitting) occur prior to any heating or cooking step. Unfortunately, the often intensive processing, especially heating, tends to change the character of the produce to other than its natural state. While this may be desirable in some cases, such as in pickling cucumbers, the result with canned fruits can be extremely disappointing.
Preserved fruit, more commonly referred to in United States markets as canned fruit, usually comprise between 10 and 25% by weight of sugar, but higher concentrations up to above 30% by weight can occasionally be reached. The sugar in the syrup for canned fruit serves primarily for sweetening, but also to improve the aroma and fruitiness. The conventional measure of the sugar content of a solution or fruit is Brix, with units in degrees (° Bx). One degree Brix is 1 gram of sucrose in 100 grams of solution/fruit and represents the sugar strength as percentage by weight (% w/w).
Despite the long history of advances in canning methods, there remains a need for an improved method for preparing fresh whole fruits, especially berries, that preserves the fruit in large part in its natural state.